Die shaving wrought copper and its alloys



Oct. 16, 1962 .1. M. KELLY ETAL 3,058,197

Filed June 14, .1960v 2 Sheets-Sheet l :2o -so Z 2 o I00 6 S [D RC g 90- -50 u z I O 3 so- -40 Lu 0 2 0 7o -30 0: 4 LL! I U 60- -2o 35 0.

40 l I l l I l l DIE RADIUS-R WITNESSES Fig. 3. INVENTORS James M. Kelly, Edward P. Kelly and Herman H. Schmifl.

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ATTORNEY waited rates Fatent 3,058,197 Patented Oct. 16, 1962 fire 3,058,197 DIE SHAVENG WRUUGHT COPPER AND ITS ALLOYS .larnes M. Keily, Traficrd, Edward P. Kelly, Irwin, and

Herman H. Schmitt, Parker, Pa, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Fiied June 14, 1960, Ser. No. 36,083 6 Qiaims. (Cl. 29-953) This invention relates to apparatus and the technique, or process, of shaving wrought metals, particularly copper and its alloys.

Wrought copper products used in the electrical indus tries are, in general, formed to desired size and shaped by:

(1) Casting wire bar; (2) Hot rolling; and (3) Cold rolling.

Subsequently as a fourth step the finished product is drawn through dies to dimension. Also certain modifications of the mentioned procedures are known as extrusion instead of hot rolling.

The mentioned procedures lend themselves to production line use and have for years produced reasonably satisfactory copper products that have been accepted in the electrical industry and allied applications.

Recent trends in the electrical industry have raised the standard of acceptance and now a much improved Wrought copper product, particularly with reference to surface finish, dimension, general appearance, and reliability in use, must be provided.

Further, new type insulations, new designs of electrical apparatus, increased current loading per unit of weight and higher current ratings, demand wrought copper products free from slivers, surface inclusions, copper dust, rolled in and drawn oxides, and stain, etc., inherently common to a variable degree in most copper processed by the techniques hereinabove mentioned.

One broad object of this invention is proper die shaving of the bars, rods, or wires of copper and its alloys and similar metals.

The process of die shaving is the removal of surface blemishes and material from one, or more, or all the surfaces of the wrought copper product thus yielding a product of excellent surface finish, close dimensional tolerance and high metal lustre. This is so because the very nature of forming the bars and rods places the blemishes in the surface. Rolling or drawing through a die tends to increase rather than decrease the surface blemish.

It has been known for some time that the removal of the surface layer from a copper rod, or bar, would improve its appearance, and reliability in use. Surface grinding had been tried but such a procedure is rather expensive.

Die shaving has been tried in the past with some measure of suceess, but never with a consistent reliable result.

At one time it was thought a blunt-nosed die for surface shaving was desired. This type of die pushed and rubbed the copper rod surface rather than shaved off a selected layer as was intended.

At other times a die with a sharp cutting edge was used and still no consistent reliable results were obtained.

This indicated that the basic factors that contributed to the results were not fully understood, and that no consistent reliable results can be obtained as long as the method of attack is one of trial and error.

The inventors have made exhaustive studies to get at the basic factors involved to obtain consistent reliable results. Their studies reveal the basic key to successful shaving and shaving die design concerns itself with, (1) the radius on the cutting, or shaving, edge of the die, (2) the relation of the hardness of the material to be shaved to this radius, (3) the die clearance and the method of providing this clearance, (4) and the support and the alignment of the material to be shaved.

In the drawings:

FIG. 1 shows a very much enlarged sectional view of the cutting edge of the shave die;

FIG. 2 is a showing helpful in disclosing the cutting, or shaving, edge of the shaving die;

FIG. 3 shows a curve helpful in disclosing this invention; and

FIG. 4 shows a longitudinal sectional view of a complete shaving die.

FIG. 1 shows an insert AC of tool steel, tungsten carbide, or other suitable hard and tough cutting material, in the body of the die. The importance of the radius of curvature at the cutting edge cannot be overstressed or overemphasized, because the proper grinding and forming of this radius, its location in respect to the cutting edge CE and its physical size are important to successful shaving operation.

FIG. 2, drawn to a smaller scale than FIG. 1, will perhaps be helpful in disclosing the radius in question. Two lines x-x and yy are drawn as shown. The circle is added from the center 0, the intersection of the lines. The radius of this circle is chosen to be the radius giving the best performance of the cutting tool, or die, in relation to the hardness of the wrought copper to be shaved. In other words, this radius is R shown in FIG. 1 and the cuting edge of the shave die is the point A, the intersection between the circle and line x-x.

The physical size of this radius in inches has been found to be directly related to the hardness of the wrought copper to be shaved. The curve shown in FIG. 3 shows this relation.

For unworked copper, that is, copper having no cold reduction and having a hardness of 40 as seen in FIG. 3, the length of the radius has to be .0302 of an inch and no greater radius R will do. From FIG. 3, it is apparent that the amount of cold reduction also determines the hardness. To show this relation the percent cold reduction is shown at the right and the hardness scale at the left. Unusually the copper has received some cold reduction in area before it gets to the mill for shaving. In fact, this reduction in area may be well over the 50%.

Assuming that the reduction in area from the cold Working is 60%. This corresponds to a hardness number of 100. The very best radius R for the cutting edge CE is one of .0225 inch. This is, however, not too critical. What FIG. 3 actually shows that in no case should the radius R be less than .02 of an inch nor more than .0302 of an inch. Within this range there is thus some choice. The best radius to use for a copper of a particular hardness is the radius indicated by curve RC, but as long as the radius falls within the range .02 of an inch and .0302 of an inch coppers of a fairly wide range of hardness can be properly shaved.

Now the die must also have a clearance so that no parts of it act as a wire die, that is, a cold reduction die. From FIG. 1 it will be apparent that the radius R emanates from a center that is the same distance from the axis of the die as the cutting edge CE, considering a die for a cylindrical rod CR, is from the axis of the die. Or in other words it emanates from the surface of the shaved rod CR. From the front of the cutting edge toward the rear, the die has a small but increasing clearance C. This clearance, while not too critical, cannot be chosen at random, and for proper consistent results increases from Zero at the cutting edge to from .025 of an inch per inch distance from the cutting edge toward the rear to .032 of an inch per inch distance toward the rear from the Cutting edge. This means the inner surface of a circular die is in the shape of a frustum of a cone with the angle between the axis of the cone and a straight line in the surface of the cone and intersecting the axis, having an average angle of 1 38', and a range of about twelve minutes of an are above or below this average angle.

The die D has the annular cutting insert AC and the curvature at region CU above, or removed, from the cutting edge CE, is so shaped by suitable grinding to provide a reverse curve for the proper breaking of the shaved material into small chips, CH.

In operation the die, shown complete in axial section in FIG. 4, is rigidly mounted in a suitable wire, rod or bar drawing machine and the part to be shaved, as cylindrical rod CR is drawn through the die with the axis of the rod in coincidence with the axis of the die.

The relationship the radius should have to the hardness of the copper above described may be amplified by consideriug for soft copper, substantially unworked copper,

Vickers Hardness Number 40 Radius .020

Thus, it can be stated that so long as the ratio of the Vickers hardness number to the shaving die radius is within the numerical range of 1323 to 6000 successful shaving results are achieved.

Since :the radius is rather small and the insert AC is of extremely hard and tough material the radius is formed by the use of diamond dust and a suitable lapping technique.

The technique hereinabove described is not limited to the simple shape shown in FIG. 4, nor is the procedure confined to basic copper. A variety of metals as aluminum, nickel, etc., and their alloys could be processed in the manner herein disclosed.

In practice bars, as rods and wires circular in transverse section need shaving most frequently. Also often bars having a transverse section that is either square, oval, or rectangular need to be shaved. The invention is, of course, not limited to a bar having a particular transverse section. The die properly shaped at the cutting edge and the proper clearance of the rear of the cutting edge, lends itself to the shaving of one or more surfaces of bars that have any one of the following transverse cross sections: C-shaped, D-shaped, H-shaped, T-shaped, etc.

Extruded shapes where finish and dimension tolerance is not sufliciently exacting are ideal applications for direct subsequent shaving procedure. Soft coppers may, with the die herein disclosed, be shaped to precision tolerance and provided with excellent surface finish without hot rolling, cold rolling and subsequent draw-anneal procedures.

All these suggested dies and alternate procedures fall within the scope of this invention.

We claim as our invention:

1. A cutting die for shaving a surface layer off of a metal bar, a cutting edge on the die conforming generally to the transverse peripheral shape of the said metal bar that is to be shaved by moving said metal bar perpendicularly toward the cutting edge of the die, said cutting edge being shaped at the front thereof to a curvature determined by a circle whose center lies less than .0302 of an inch from the cutting edge and the radius of the center of the circle determining the curvature lies substantially in the intersection line of the shaved surface of the metal being shaved and a plane perpendicular to the shaved surface of the metal being shaved.

2. In a die for shaving a surface layer off of a metal bar, a cutting edge on the die conforming generally to the transverse peripheral shape of the said metal bar that is to be shaved by moving said metal bar perpendicularly toward the cutting edge of the die, said cutting edge being shaped at the front thereof to a curvature determined by a circle whose center lies less than .0302 of an inch from the cutting edge and the radius of the center of the circle determining the curvature lies substantially in the intersection line of the shaved surface of the metal being shaved and a plane perpendicular to the shaved surface of the metal being shaved, said die having an increasing clearance from the cutting edge toward the rear between the die and the material being shaved that increases per inch distance toward the rear from the cutting edge no less than a selected relatively small distance.

3. In a die for shaving a surface layer off of a metal bar, a cutting edge on the die conforming generally to the transverse peripheral shape of the said metal bar that is to be shaved by moving said metal bar perpendicularly toward the cutting edge of the die, said cutting edge being shaped at the front thereof to a curvature determined by a circle Whose center lies less than .0302 of an inch from the cutting edge and the radius of the center of the circle determining the curvature lies substantially in the intersection line of the shaved surface of the metal being shaved and a plane perpendicular to the shaved surface of the metal being shaved, said die having an increasing clearance from the cutting edge toward the rear between the die and the material being shaved that increases from no less than .025 of an inch to no more than .032 of an inch per inch distance from the cutting edge toward the rear.

4. In a die for shaving a surface layer off of a metal bar, a cutting edge on the die conforming generally to the transverse shape of the said metal bar that is to be shaved by moving said metal bar perpendicularly toward the cutting edge of the die, said die being shaped at the front of the cutting edge to a curvature determined by a circle whose center lies less than .0302 of an inch from the cutting edge and the radius of the center of the circle determining the curvature lies substantially in the intersection line of the shaved surface of the metal being shaved and a plane perpendicular to the shaved surface of the metal being shaved, said die having an increasing clearance from the cutting edge toward the rear between the die and the material being shaved that increases per inch distance toward the rear from the cutting edge no less than a distance of .025 of an inch.

5. An annular die for shaving a surface layer off of a metal rod, said die having a front circular cutting edge of a selected radial dimension with the inner surface being that of a frustum of a cone with the portion with the larger diameter flaring outwardly by a relatively small angle, as from a fraction of a degree to no more than a very few degrees, and the cutting edge in any longitudinal sectional plane including the axis of the frustum of the cone has a curvature at the front away from the cutting that is determined by a radius no greater than .0302 of an inch and Whose center, or rear end, falls at a point away from the axis of the cone a distance equal to the radius of the circular cutting edge.

5 6. A shaving die for shaving a surface layer of a selected thickness 011 of the surface of a bar of metal, said die having a cutting edge which at its front curves away from the metal being shaved on a radius parallel to the shaved metal surface and whose length may be 5 2,679,680

selectively varied from .020 of an inch for relatively hard and well cold worked metal to .0302 of an inch for substantially unworked metal, said die having a clearance between the die and the shaved metal that may be selectively varied from .025 of an inch to .032 of an inch per 10 inch distance toward the rear from the cutting edge.

References Cited in the file of this patent UNITED STATES PATENTS 2,392,481 Kaplan et a1 Jan. 8, 1946 Hanks June 1, 1954 FOREIGN PATENTS 505,442 Great Britain May 10, 1939 OTHER REFERENCES American Machinist, pages 190-494, March 12, 1956. 

1. A CUTTING DIE FOR SHAVING A SURFACE LAYER OFF OF A METAL BAR, A CUTTING EDGE ON THE DIE COMFORMING GENERALLY TO THE TRANSVERSE PERIPHERAL SHAPE OF THE SAID METAL BAR THAT IS TO BE SHAVED BY MOVING SAID METAL BAR PERPENDIC- 